Conventionally, as one of methods for producing concrete products, a centrifugal casting method is known and the machine used for the method comprises a rotary assembled body which is constructed by assembling a plurality of casting frames as an integral unit and such rotary assembled body is rotated at a high speed by a rotating mechanism.
The other type of the machine comprises a rotary drum which is rotated at a high speed by a rotating mechanism and a multiplicity of casting frames are mounted on the inner surface of the rotary drum.
For producing the concrete products, concrete slurry is charged into the rotary assembled body or the rotary drum by way of a feeder chute or a screw feeder which has the front end thereof disposed within the rotary assembled body or the rotary drum while the rotary assembled body or the rotary drum is being rotated at a high speed.
Due to the above rotation of the rotary assembled body or the rotary drum, a centrifugal force is exerted on the charged cement slurry and the cement slurry is filled in a plurality of concrete-slurry casting spaces defined by the casting frames.
After the above casting operation, the cement slurry filled in the concrete-slurry casting space is hardened and cured for a desired period and concrete products are removed from the concrete-slurry casting spaces.
With the above former type of the centrifugal casting machine, however, in each casting operation, the casting frames must be assembled one to the other and such assembling operation is considerably cumbersome and time-consuming.
Furthermore, since the rotary assembled body must withstand an extremely large centrifugal force during the casting operation, the structure of the rotary assembled body becomes complicated and heavy and consumes a considerable amount of energy or power for the rotation thereof. Still furthermore, since the rotary assembled body is mounted on the rotating machine by a plurality of mounting arms, the size of the rotary assembled body is restricted.
With the latter type of the centrifugal casting machines, the casting frames must be mounted on the inner surface of the rotary drum before the casting operation and the casting frames must be dismounted from the inner surface of the rotary drum to remove the concrete products from the rotary drum after the casting operation. Whereas, since the casting frames are mounted on the inner surface of the rotary drum without any positioning and fixing guide means, the mounting of such casting frames is, in general, very cumbersome and time-consuming. The same goes to the dismounting of the casting frames from the inner wall of the rotary drum.
Furthermore, during the casting operation, the concrete slurry is filled in the casting spaces with a considerable centrifugal force so that the concrete products, after being hardened, firmly adhere to the inner surfaces of the outer frames or outer surfaces of the cores. Accordingly, during the dismounting of the outer frames or the cores to take out the concrete products from the rotary drum, the removal of the concrete products becomes extremely difficult when the concrete products are considerably heavy ones.
Accordingly, it is an object of the present invention to provide a casting frame structure of a centrifugal casting machine which can resolve the above defects of conventional casting frame structures so as to enable the prompt or ready mounting and removal of the casting frames on or from the inner wall of the rotary drum thus enabling the mass-production of the concrete products.
It is another object of the present invention to provide a casting frame structure of a centrifugal casting machine which can produce the concrete products of high quality and high precision which are completely free from ruptures or cracks.